1. Field of the Invention
The invention relates to a shaft-to-universal joint coupling structure.
2. Description of the Related Art
Examples of conventional shaft-to-universal joint coupling structures include a coupling structure for coupling a column shaft of a steering shaft to a universal joint. Japanese Utility Model Application Publication No. 5-89963 describes an example of a conventional shaft-to-universal joint coupling structure.
FIG. 8 illustrates a coupling structure for coupling a universal joint 200 to a column shaft 220. The column shaft 220 is inserted into a yoke 210 of the universal joint 200. The yoke 210 and the column shaft 220 are coupled to each other with a coupling pin 230. The coupling pin 230 is press-fitted in a through-hole 221 of the column shaft 220. Opposite end portions of the coupling pin 230 are respectively inserted into insertion holes 211 of the yoke 210.
The operation of a steering member (not illustrated) repeatedly applies torsional torque to the coupling pin 230, thereby loosening the coupling pin 230 that has been press-fitted in the through-hole 221. This raises a possibility that the coupling pin 230 will come out of the through-hole 221.
However, the coupling structure for coupling the universal joint 200 to the column shaft 220 includes a cap 240 fixed to the outer peripheral face of the yoke 210. The cap 240 covers the insertion holes 211 of the yoke 210 and the coupling pin 230. Thus, even if the coupling pin 230 that has been press-fitted in the through-hole 221 loosens, the cap 240 restricts movement of the coupling pin 230, thereby preventing the coupling pin 230 from coming out of the through-hole 221.
Because the conventional coupling structure for coupling the universal joint 200 to the column shaft 220 includes the cap 240, the number of components and the number of man-hours required for assembly increase. Such increases in the number of components and the number of man-hours required for assembly may occur not only in a coupling structure for coupling a column shaft to a universal joint but also in a coupling structure for coupling an intermediate shaft of a steering shaft to a universal joint, a coupling structure for coupling a pinion shaft of a steering shaft to a universal joint, a coupling structure for coupling a drive shaft to a universal joint, and a coupling structure for coupling a propeller shaft to a universal joint.